Liftoff characteristics of turbulent jet diffusion flames

摘要: A theoretical analysis of turbulent jet diffusion flames is developed in which the flame regarded as an ensemble laminar flamelets that are highly distorted. The flow inhomogeneities considered to be sufficiently strong produce local quenching events for a consequence excessive stretch. condition flamelet extinction derived terms instantaneous scalar dissipation rate, ascribed log-normal distribution. Percolation theory random network stoichiometri c sheets used predict thresholds define liftoff heights. Predictions shown reasonably satisfactory agreement with experimentally measured heights methane flames, within experimental uncertainties. UEL issuing from tube or duct into oxidizing atmosphere forms combustion may occur. associated process most classical example flame. At high velocities fuel (fundamentally, at large Reynolds numbers) entire turbulent. begins mouth range values exit velocity. When critical velocity exceeded, abruptly detached and acquires new configuration stabilization number diameters downstream. Flames this state, stabilized mixing region, termed lifted they appear called height centerline distance plane stabilization. further increase increases without significantly modifying (the which, on average, ceases). There second value velocity, blowoff beyond cannot region. present study addresses questions structure between values. Attention focused especially calculation Liftoff characteristics practical importance connection Conditions must known developing rational designs burners, e.g., diffusion-flame combustors power production flaring applications petroleum industry. They also interest extinguishment certain fires occur oil gas rigs. work directed toward improved fundamental understanding phenomena later prove useful these applications.